A few years ago, I ran across Dan Cervelli’s excellent Closed Contour map of the Sierra. At the time I was just getting started with CalTopo and learning my way around GIS, and Closed Contour really opened my eyes to the cool stuff you can do with Mapnik. I had no idea it was so simple to take some shapefile data, add a few rendering commands, and then boom, beautiful looking maps. At least, the tools are that simple – obviously there’s still a lot of talent and hard work involved in producing the final product.

The original Closed Contour map was built on a projection and tiling system incompatible with Google Maps, so integration into the universe of sites and apps using that as a de-facto standard was not possible. Dan has a new Yosemite map built around this standard, and I thought it would make a great end-to-end demo of some things CalTopo can do with “web mercator” tile sets.

Step 1: Add a Custom LayerThe more maps, the better – CalTopo is built around the idea of combining different map layers into a single coherent picture. Unfortunately, I have to balance supplying layers of regional or special interest against providing a reasonably compact, easy to navigate UI. The middle ground I’ve settled on is to make it easy to add custom layers from a tile URL or WMS address. You can also choose from a preset list of useful layers, which Closed Contour has now joined:

Closed Contour now appears in the layer dropdown alongside the standard CalTopo layers

and provides a snazzy backdrop for some route planning, complete with trail mileages